Hello Hans; I would go with the Saito 45S, it will have plenty of power for the Kadet. I have 2 45S' and like them quite a bit. I think that Saito write that in their instructions so that people aren't expecting overwhelming power out of it. I have a 45 that I used for over ten years in our club trainer, a PT40. The "S" version has more power then the earlier 45s. I also have 3 50s, and like them too, but I think you'll be happy with the 45S. It seems to me that most people that post on this forum like to over-power their planes, I guess the feeling is "I can always throttle back", or maybe they have high altitude to deal with, which would need more power. I fly at sea level, and seem to get better performance then is usually reported here. We have had a few Kadets at our field, usually with 40 two strokes, one I remember had a K and B 29 sportster in it, it flew along just fine, took off in a reasonable distance.

I also have a Saito 56 for a Gee whiz Bee that I'm finishing off right now. I flew that engine in my Sig Ultimate fun fly until someone saw it flying and had to buy it. I liked that plane so when he asked me how much it would take to buy it from me, I told him a ridiculous price ($275), He just wrote out the cheque to me, so I took the servos and engine out and gave it to him. I wish I hadn't.